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bbq
11-19-2015, 04:20 PM
Dear Experts,

I am a big fan of JBL vintage and more speakers I try more I like the sound, I started with L36 then L112 and now I purchased a pair of Dorian C56 in need of restoration job. First thing is the tweeter not working and I know these LE175DLH are built like a tank so I suspected the crossover, when I opened one of them I found the E core inductor coil wet with some kind of oil and the capacitor also seem to be leaking oil as shown on the pic. I would like to replace these components and I started by downloading the schematic of LX10:
1. should I replace everything: C1 (12 uF), L1 (0.9 mH) and R1 (5.1 ohm), R2 (7.5 ohm)???
2. On the drawing first page, I read C1 12 uF but on the second page bill of material I see item 11. Part Number 10434 CAPACITOR .12 uF (is this C1 0.12 uF or 12 uF???)
3. If it is 12 uF which voltage rating should I pick 250, 400 or 800V? can I go little higher as 15 uF, how will this affect?
4. Can I replace the existing ferrite E Core inductor with an Air core coil ( copper foil coil or solid core coil as other options?)
5. Resistors R1 (5.1 ohm), R2 (7.5 ohm), can I pick the 10W?

Thanks and best regards
A. D.

badman
11-19-2015, 04:28 PM
Dear Experts,

I am a big fan of JBL vintage and more speakers I try more I like the sound, I started with L36 then L112 and now I purchased a pair of Dorian C56 in need of restoration job. First thing is the tweeter not working and I know these LE175DLH are built like a tank so I suspected the crossover, when I opened one of them I found the E core inductor coil wet with some kind of oil and the capacitor also seem to be leaking oil as shown on the pic. I would like to replace these components and I started by downloading the schematic of LX10:
1. should I replace everything: C1 (12 uF), L1 (0.9 mH) and R1 (5.1 ohm), R2 (7.5 ohm)???
2. On the drawing first page, I read C1 12 uF but on the second page bill of material I see item 11. Part Number 10434 CAPACITOR .12 uF (is this C1 0.12 uF or 12 uF???)
3. If it is 12 uF which voltage rating should I pick 250, 400 or 800V? can I go little higher as 15 uF, how will this affect?
4. Can I replace the existing ferrite E Core inductor with an Air core coil ( copper foil coil or solid core coil as other options?)
5. Resistors R1 (5.1 ohm), R2 (7.5 ohm), can I pick the 10W?

Thanks and best regards
A. D.

1. Most likely just the cap needs replacement*
2. 12uF is definitely the value, based on normal cap sizes used in XOs and the physical size of the cap
3. Any voltage is fine. Speakers rarely see >20V, so 100V is the usual minimum voltage used
4. Not now- you'd want to match the DCR in any case. I prefer aircores but first get it working. It's unlikely the coil or resistors are substantially off-spec.
5. Go big on resistors. 20W+, more the better, but they don't likely need replacement now.

*The L-Pad is a likely candidate for replacement, those as moving parts often go south.

bbq
11-20-2015, 10:36 AM
1. Most likely just the cap needs replacement*
2. 12uF is definitely the value, based on normal cap sizes used in XOs and the physical size of the cap
............i am going with 12 uF 400V, please confirm?, would it be better to use 15 uF 800 VDC (or 1200 VDC)

4. Not now- you'd want to match the DCR in any case. I prefer aircores but first get it working. It's unlikely the coil or resistors are substantially off-spec.
...........I am getting a 0.90mH 18 AWG Air Core inductor crossover coil, please confirm this is correct? ......I want to get one shipment from part express in case I need a total upgrade.

5. Go big on resistors. 20W+, more the better, but they don't likely need replacement now.
...........I tested both of them and they read much less than 5.1 and 7.5 ohm so I am getting both resistors replacement with 10W for both...I didn't find anything more than 10W at part express.

*The L-Pad is a likely candidate for replacement, those as moving parts often go south.
............Please confirm if the L-Pad is 100W Mono 1" shaft 8 ohmBest regards
A. D.

Wagner
11-20-2015, 12:19 PM
I would NOT replace that L-pad unless it was confirmed to be bad or damaged
Disassemble and clean properly, treat the contact areas appropriately and you're good to go for another 30 years of trouble free, noise free operation
It is very difficult to find anything today that equals or exceeds the quality of those Japanese built pads that JBL used to use and that will fit properly without jumping through hoops

Some (as in many) of the brand new ones I have had to use have been staticky right out of the box (required DeOxit) and that includes the every popular Parts Express offerings

The "COSMOS" and "Alps" branded pots are better than anything you're going to find today unless you go WAY UP THE PAY SCALE and are able to find some sort of sealed Mil Spec pad (and that's not likely)

That, or build a stepped attenuator

Unless they are damaged or burned, save/use the old ones (after inspecting them thoroughly of course)

My experience and opinion

gsb001
12-01-2015, 06:02 AM
I have a pair of original UN-restored, C56 Dorian's with the marble top and lattice grilles.
Do you have restoration plans for the cabinets and grilles too?
SB